In a passionate attack on Salmond’s plans at Kilmarnock FC’s ground, Brown accused the Yes campaign of using the NHS to frighten people into voting for separation.

Speaking without notes, the Kirkcaldy and Cowdenbeath MP told a Labour rally that Salmond “wants to continue to tell you that he is powerless to do anything about the National Health Service while he is First Minister of Scotland under the existing powers of the Scottish ­Parliament”.

He added: “If he continues to peddle that lie, let him make way for the Labour Party and we will run the health service properly.

Gordon Brown with local MP Cathy Jamieson at Kilmarnock Football Club

“And I say this to Mr Salmond himself, until today, I am outside frontline politics.

“If he continues to peddle this ­deception that he cannot do anything to improve the health service until he has a separate state, then I will want to join Johann Lamont in fighting him and securing the return of a Labour ­government.”

Brown took charge of the No campaign after a shock poll over the weekend showed that more voters were planning to vote for independence than against it.

He has been credited with helping turn around the fortunes of the unionists after a Daily Record poll yesterday put the No campaign six points ahead of Yes.

Brown said: “The SNP and these ­nationalists don’t go to sleep at night worrying about the NHS and how to advance it. They go to sleep worrying about the SNP and how it can advance.

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“They don’t wake up in the morning thinking about how they can save the National Health service.

“They wake up at the moment thinking about how they can use the National Health Service as a Trojan horse for getting their own policy through, which is a ­ separate state.”

The NHS become a major issue late on in the referendum campaign after Salmond started claiming a No vote would put it under threat.

While the First Minister’s claims have been dismissed by experts, doctors and nurses, they have been credited with winning the Yes side referendum votes.

There has been repeated speculation that Brown intends to stand down as an MP at the next election.

That could leave him free to stand at Holyrood in 2016.

SNP MSP Derek Mackay said: “Gordon Brown’s attempt to use the independence referendum as a springboard for his own political career speaks volumes.

“The referendum on Scotland’s future is bigger than any individual or any political party – something Mr Brown has patently failed to grasp.

“Only a Yes vote and independence will give Scotland the job-creating powers we need, safeguard the long-term future of the NHS and make sure that we always get the governments we vote for – and guarantee that we never again are ruled by Tory governments we didn’t vote for.”